CONSTANT CURRENT DRIVING CIRCUIT, ELECTRONIC DEVICE USING THE SAME, AND METHOD FOR DRIVING LIGHT EMITTING DIODE

PROBLEM TO BE SOLVED: To provide a constant current driving circuit for stably driving a load using a large current. SOLUTION: The constant current driving circuit 100 drives the LED 50a-50c using the first current Idrv1, and drives the LED 50d using the second current Idrv2 larger than the first current Idrv1. A charge pump circuit 10 is switched among a plurality of a voltage boosting rate. Constant current circuits 20a-20d are provided on driving paths of the LED 50a-50d. A monitoring circuit 24 monitors voltages across the constant current circuit 20a-20c. When the LED 50a-50c are driven and a voltage monitored by the monitoring circuit 24 is below a threshold voltage Vth, a state machine 22 increases the voltage boosting rate. Before the LED 50d is driven, the state machine 22 doubles the voltage boosting rate of the charge pump circuit 10 regardless of a result monitored by the monitoring circuit 24. After the LED 50d is driven, the state machine 22 resets the voltage boosting rate to one time. COPYRIGHT: (C)2007,JPO&INPIT